Composite Confinement Systems for RC Column Repair and Construction under Seismic Loads: Concept, Characterization and Performanc

This study aims at developing, characterizing and validating an integrated composite confinement system of conventional jackets for: (1) repair and retrofit of existing bridge columns; and (2) construction of new bridge columns, subjected to earthquake excitations.;A new composite steel confinement jacket was proposed by combining a thin steel sheet and prestressing strands as a hybrid jacket, incorporating active and passive confining pressure on damaged RC columns. Both experimental and analytical studies were conducted to understand the performance and effectiveness of the proposed repair method. The experimental study involved two ½-scale lap-spliced deficient RC bridge columns originally tested to failure under reversed cyclic loading. The proposed jacket was designed and implemented to repair the damaged columns to achieve the required performance level after repair intervention for service and ultimate limit states. Experimental results indicated that both repaired columns exceeded the strength and ductility of their as-built columns. The stiffness of the second column designed for ultimate limit state was completely restored. Analytical studies and collapse analyses on the seismic performance of post-mainshock repaired bridges subjected to mainshock-aftershock sequences demonstrated the efficacy of the proposed technique under severe mainshock-severe aftershock attacks.;Another new composite confinement system of a fiber reinforced polymer (FRP) sheet wrapped around a polyvinyl chloride (PVC) tube with energy dissipation medium in between was developed for new bridge columns construction. This composite system is essentially a FRP-confined concrete-filled PVC tube, featuring exceptional durability properties of PVC materials in addition to high strength of the FRP fabrics. Experimental tests under uniaxial compression and flexural loading were undertaken to establish the representative stress-strain behavior of confined concrete filled PVC tubes (CCFPT). Experimental studies clearly demonstrated that the CCFPT system outperforms conventional FRP jacket. The intermediate energy dissipation medium is critical to make the post-peak behavior more ductile. Analytical studies were conducted and equations were derived for the prediction of the ultimate strength and strain of a CCFPT system.